CPU use is going to vary greatly depending on the game and the operating system you're using (and even the GPU and driver version to some degree).
The massive majority of DX11 and DX9 games can only really use two cores for rendering, which is where the workload really is, and then another for the game's logic and simulation threads. Since you have 6 cores, most games are only going to use 33% for rendering and a bit more for everything else meaning your overall CPU use will likely be around 30 to 50% the majority of the time. Windows 8.1 and Windows 10 will bounce those threads around across your available cores but overall load will still not go up.
DX12 and Vulkan based games will use all available cores and with those you'll see higher overall usage (assuming the developer made use of that feature correctly which so far several haven't).
As with any "rule" there are always exceptions of course but the majority of the time your overall load will be where you're seeing it with games